The present invention relates to a method and apparatus for air conditioning motor vehicles.
The presently used systems for air conditioning motor vehicles usually include a compressor for increasing the pressure of the refrigerant gas to a point where liquefaction may occur in the condenser. Compressor-type air conditioners, however, have a number of drawbacks when used in motor vehicles. One serious drawback is that they reduce the driving power output of the vehicle engine to such an extent that compressor-type air conditioners can normally be used only with automobiles having relatively large engines. In addition, compressor-type air conditioners increase the fuel consumption as much as 15% or 20%. Further, they are relatively expensive and require continuous maintenance.
There have been prior proposals to air condition motor vehicles by the use of absorption-type systems, wherein heat, rather than mechanical work, is used as the primary energy source for the refrigeration cycle. These previously proposed absorption-type air conditioners generally used heat-exchangers for extracting heat, either from the vehicle radiator, or from the hot engine exhaust gases, or from both. However, they were generally found not commercially satisfactory for a number of reasons. Thus, the extraction of heat from hot exhaust gases requires a large heat transfer area. In addition, heat-exchangers produce a pressure drop in the vehicle exhaust pipe system, thereby reducing engine efficiency. Further, the extraction of heat from hot exhaust gases produces serious corrosion problems.
On the other hand, it has been found impractical to utilize the radiator as a sole source of energy because of its relatively low temperature, although the quantity of heat present there is quite high.